My Lumia 920 both front and back camera are not working and my microphone too but the phone sound is working perfectly so please give me a quick solution for this problem

There is no quick solution for that problem. Which mic does not work? The mic for phone calls or video/audio recording?

For all three of those to be failing at the same time it's most likely a hardware issue. Either you dropped the phone and items inside came loose. Or they failed all together for some other reason. I'd open the back cover to see if anything happened. If nothing looks out of place you're better off backing up your phone and trying a hard reset to see if that helps. If no go there the hardware failed some how.

My Lumia 920 both front and back camera are not working and my microphone too but the phone sound is working perfectly so please give me a quick solution for this problem

There is no fast answer for that issue. Which mic does not work? The mic for telephone calls or video/sound chronicle?

For every one of the three of those to bomb in the meantime it's undoubtedly an equipment issue. It is possible that you dropped the telephone and things inside came free. Or on the other hand they bombed all together for some other reason. I'd open the back cover to check whether anything occurred. In the event that nothing watches strange you're in an ideal situation backing up your telephone and making a decent attempt reset to check whether that makes a difference. On the off chance that no go there the equipment bombed some how.